The invention relates to the field of accelerometers and more particularly to an assembly for supporting a force sensing pendulum in an accelerometer.
It has been a continuing problem in the design of accelerometers that use pivotally supported, force responsive pendulums to provide a support assembly that minimizes rotational friction while at the same time providing rigid support for the pendulum so that lateral movement of the pendulum with respect to the support frame of the accelerometer is eliminated insofar as possible. For accurate calibration of this type of accelerometer it is necessary that the optimum pressure or preload be applied through the bearing rotationally supporting the pendulum so as to minimize rotational friction while providing adequate lateral support of the pendulum. Sufficient lateral support of the pendulum is necessary in order to insure that the pendulum is properly aligned within the accelerometer and that wear is minimized in the bearing that provides rotational support for the pendulum.
In prior art accelerometer flexure assemblies, as illustrated by U.S. Pats. to Clark Nos. 3,246,525 and to Hugli et al 4,131,020, there has not been a really effective way of accurately adjusting the preload force on the flexure or flexures supporting the bearings that in turn support the pendulum axles. In Clark U.S. Pat. No. 3,246,525 for example, two cantilevered flexures or supports are provided wherein the contact pressure on the pendulum pivot pins is set by varying the spring stiffness of the flexures. Aside from the apparent inaccuracies in such a procedure, the flexure assembly shown in Clark U.S. Pat. No. 3,246,525 is subject to alignment errors as well as potential problems from vibration resulting from the natural resonant frequency of the two cantilevered flexures. In Hugli et al U.S. Pat. No. 4,131,020 a single flexure is clamped at both ends with the preload being set by a screw thereby making it difficult to directly determine the preload force on the flexure. In this arrangement the preload is typically determined indirectly by measuring friction torque or the play between pivot and bearing.